Answer:
Increased:
Rate of the forward reaction
Rate of the reverse reaction
Decreased:
Activation energy of the forward reaction
Activation energy of the reverse reaction
Explanation:
Consider the following diagram, which depicts the energies of the reaction components over time.
Note that the identities of the reactants and products are the same for both the catalyzed and uncatalyzed reactions. In other words, the catalyst has no effect on the overall reaction. Since enthalpy is is the difference between the energy of the products and the reactants, the enthalpy is also unaffected by the catalyst, because the reactants and the products have the same energy in the catalyzed and uncatalyzed reactions.
Activation energy can be thought of as a hindrance to reaction progress. A higher activation energy results in a slower reaction. A catalyst increases the rate of both the forward and the reverse reactions by providing an alternate path of lower activation energy in either direction.
Notice that the difference between the energy of the reactants and the transition state is lower for the catalyzed reaction than it is for the uncatalyzed reaction, illustrating that a catalyst decreases with the activation energy of the forward reaction.
Also, notice that the difference between the energy of the products and the transition state is lower for the catalyzed reactant that it is for the uncatalyzed reaction, illustrating that a catalyst decreases the activation energy of the reverse reaction.
A catalyst is able to lower the activation energy of a reaction because it provides an alternate path or mechanism with lower energy transition states. In the diagram, this is depicted by the two humps in the catalyzed reaction, representing two steps and two transition states, as opposed to one hump (one step one transition state) in the uncatalyzed reaction.
